1. Field of the Invention
This invention relates generally to handling wound rolls of material and, in particular, for determining the internal structure of a wound roll.
2. Background of the Invention
In industries, such as the printing industry, that utilize wound rolls (xe2x80x9cwebsxe2x80x9d) of material, it is advantageous to be able to determine the internal structure of such rolls. Before time and resources are directed to converting a wound roll of material into a finished product, a determination of the wound roll""s internal structure allows a processor to know whether the wound roll is of sufficient quality to warrant conversion. Structural characterization of a roll also helps ensure that problematic wound rolls that could damage sensitive machinery are not processed.
One standard approach in the prior art to determining the internal structure of a wound roll is to use a device based on a split hopkinson pressure bar in order to measure the time of flight of mechanical energy through the roll. A split hopkinson pressure bar consists of two projectiles located within a hollow tube. The first projectile is a simple cylindrical plug of material that is free to travel within the tube. The second projectile is located at one end of the tube and can move only within a narrow range inside the tube. In operation, one end of the second projectile is in contact with the wound roll of material. To determine the internal structure of the wound roll, the first projectile is sent down the tube and impacts the second projectile. The second projectile thereupon impacts the wound roll, imparting mechanical energy thereto. A sensor records the impact of the second projectile on the wound roll.
This approach suffers from several disadvantages. First, the first projectile is susceptible to becoming jammed in the tube. This is due to the deformation of the first projectile that occurs when it impacts the second projectile. Second, the second projectile is also susceptible to becoming jammed due to the deformation of structures used to guide and retain it. As a result, each time either projectile becomes jammed, the system must be disassembled and the deformed projectile replaced.
Accordingly, there is a need for a system for imparting mechanical energy to a wound roll that is reliable, convenient to operate, and easily maintained.
An apparatus in accordance with the present invention includes a specially designed single projectile for imparting mechanical energy to a wound roll. The use of a single projectile significantly reduces its operational deformation. Moreover, the shape of the projectile ensures that all or nearly all of the projectile""s mechanical energy is transferred to the wound roll. This means that little mechanical energy remains for deformation. The projectile""s shape helps to guide it smoothly within the tube, thereby further reducing the possibility that it can become jammed, and also improves the signal-to-noise ratio. A sensor arrangement provides clear signals, and the projectile""s unibody nature simplifies replacement.
According to one aspect, the invention comprises a system for imparting and detecting mechanical energy. An embodiment of the system includes a projectile and a hollow tube allowing the projectile to move therein. A portion of the projectile is allowed to emerge from one end of the tube and thereby transfer mechanical energy to a receiving entity, e.g., a wound roll of material. An actuator drives the projectile through the tube, and a first sensor detects when the protruding portion of the projectile extends from the tube to make contact with, for example, the core of the wound roll to start a timing sequence. A second sensor detects the arrival of the mechanical energy at, for example, the roll surface so that a comparison can be made between the start and end times.
According to another aspect, the invention relates to a method of imparting and detecting mechanical energy. In one embodiment, the method comprises sending a projectile down a hollow tube from a first end to a second end thereof. The second end of the tube allows a portion of the projectile to protrude beyond the tube to transfer mechanical energy to a receiving entity. Mechanical energy from the projectile is transferred to the receiving entity, and this transfer is sensed. In addition, the method comprises sensing the transferred mechanical energy in the receiving entity. The method facilitates, and may include, calculating time-of-flight information for the mechanical energy traveling through the receiving entity.